Engines operate in a variety of operating modes responsive to environmental conditions, driver requests, etc. Some engines can operate a sub-set of cylinder in a deactivated mode, such as a fuel shut-off mode or a cylinder deactivation (intake/exhaust valves held closed) mode.
However, the inventors herein have recognized various issues with such approaches. As one example, improved efficiently and/or reduced gas flow during such deactivation modes may reduce catalyst temperature below a light-off temperature.
Additionally, engines may also operate rich during various modes to protect engine or exhaust components, such as catalyst over-temperature conditions.
Again, the inventors herein have recognized that such operation may increase exhaust emissions.
At least some of the above issues may be addressed by a method of operating an engine having an intake, an exhaust, and a hydrocarbon-retaining system, the method comprising: during warm-up conditions, routing exhaust gases of the engine to the hydrocarbon retaining system to store exhaust hydrocarbons; after warm-up conditions, purging stored hydrocarbons from the hydrocarbon-retaining system; and after purging, and during select operating conditions when the engine continues to spin, again routing exhaust gases of the engine to the hydrocarbon-retaining system.
In this way, it is possible to take advantage of the hydrocarbon-retaining system during both start-up conditions, and other operating conditions that occur after engine start and/or warm-up, such as during cylinder deactivation operation. Specifically, in this regard, it may be possible to provide greater use of cylinder deactivation, while also avoid degrading emission control effects related to reduced catalyst temperatures.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.